Nonneoplastic bone diseases

Fibro-osseous lesions

This is a nonspecific term encompassing diseases ranging from fibrous dysplasia to the well-circumscribed lesions of ossifying fibroma and uncommon, apparently intermediate, types. It is a controversial area, with diagnosis dependent on consideration of clinical and radiographic features, microscopy and behaviour.

Fibrous dysplasia (monostotic)

Typically seen in young adults of either sex as rounded, painless, smooth bony swelling of the maxilla. The swelling may disturb function or occlusion.

Radiography shows a rounded area of relative radiolucency often with fine orange peel or ground glass appearance, but lesions vary from predominantly fibrous with pseudocystic appearance to patchily sclerotic, and densely ossified. The borders merge imperceptibly with surrounding normal bone.

Microscopy Rounded mass of loose, cellular fibrous tissue, typically containing evenly distributed slender trabeculae of woven bone (Figs 120 & 121) with osteoblasts within them (Fig. 122), blending imperceptibly with normal bone trabeculae at margins. The amount of bone is highly variable. Sometimes small foci of scattered giant cells (Fig. 123) or myxoid tissue can be seen. There are no significant changes in blood chemistry.

Treatment Typically, there is a spontaneous arrest of progress with skeletal maturity. Resection is only required for disfigurement or disturbed function.

Polyostotic fibrous dysplasia

Onset is often in childhood, predominantly in females. There arc multiple lesions with macular skin pigmentation, endocrine disturbances and precocious puberty in females in Albright syndrome.

Microscopy Similar to monostotic type.

Fibrous Dysplasia

fig. 120 Fibrous dysplasia involving periodontal tissues.

Fibrous Dysplasia
Fig. 122 Fibrous dysplasia: detail of woven bone.
Monostotic Fibrous Dysplasia Maxilla

fig 123 Fibrous dysplasia: small focus of giant cetts.

Cherubism (familial fibrous dysplasia)

Resembles fibrous dysplasia in its cessation of progress after skeletal maturation but differs in:

• microscopic features

• symmetrical involvement of jaws (mandible, ramus and adjacent body; maxilla also in severe cases)

• lesions appear multicystic on radiographs

• typically regresses with skeletal maturity

• autosomal dominant inheritance but poor penetration of the trait in females and many sporadic cases. Radiolucencies precede swelling and may persist for some years after clinical resolution.

Microscopy Replacement of bone by loose vascular connective tissue containing many giant cells usually resembling giant cell granuloma (Fig. 124). Histopathology of cherubism and fibrous dysplasias is not in itself diagnostic. Confirmation depends on:

• clinical picture

• radiographic features

• behaviour of lesion.

Hyperparathyroidism

• Primary hyperparathyroidism—hypersecretion of parathormone by parathyroid tumour but bone lesions now exceedingly rare.

• Secondary hyperparathyroidism results from renal failure leading to reactive parathyroid hyperplasia.

Tumour-like foci of osteoclasts (Figs 125 & 126) produce cyst-like areas (sometimes multilocular) on radiographs (osteitis fibrosa cystica). Microscopically, the condition is indistinguishable from giant cell granuloma of the jaws. Diagnosis depends on serum chemistry changes, namely, raised calcium (up to x2 normal), normal or low phosphate and raised alkaline phosphatase.

Aetiology

Microscopy

Osteitis Deformans

Rg. 126 Hyperparathyroidism: details of osteoclasts.

Hyperparathyroidism

Rg. 12S Hyperparathyroidism

Rg. 12S Hyperparathyroidism

Rg. 126 Hyperparathyroidism: details of osteoclasts.

Paget's disease of bone (osteitis deformans)

Aetiology and May be radiologicallv detectable in 5% of those over 55 prevalence in some areas of Britain, but symptomatic deforming disease is uncommon. The aetiology is unclear but there is evidence of weak gcnetic and possibly viral components.

The condition is usually polyostotic and most frequently affects the pelvis, cal varí um and limbs. The maxilla is occasionally affectcd and the mandible only rarely. Lesions arc predominantly osteolytic initially but there is increasing sclerosis, often with gross generalized thickening of bone. Alkaline phosphatase levels are greatly raised (up to x20 normal).

Radiographically, there is variable radioluccncy of the bone of the jaws, with loss of trabeculation and lamina dura, followed by cotton-wool areas of radiopacity and gross, craggy hypcrccmentosis. In the maxilla, gross thickening of the alveolar ridges causcs the middle third of the face to bulge forward.

Microscopy Anarchic disorganization of normal bone remodelling is characteristic with alternating resorption and deposition (Fig. 127): many osteoblasts and osteoclasts line the bone margins (l:ig. 128). An irregular pattern of reversal lines produces a jigsaw-puzzle ('mosaic') pattern of basophilic lines in the bone, typically with predominant osteoclastic activity initially, but then with progressively increasing osteoblastic activity causing bones to become thicker and larger but weaker. Decreasing vascularity of bones in the late stages makes them susceptible to inlcction. Involvement of the ccmentum produces craggy hypcrcementosis, which also shows a 'mosaic' pattern microscopically (Fig. 129).

Prognosis The disease is typically active for 3-5 years but may then become virtually static.

Resting And Reversal Line Pagets Disease

fig. 127 Paget's disease of bore.

Pagets Disease The Bone Photo

fig 128 Pagefs disease of bone: 'mosaic' fig 129 Paget's disease: irregular

(reversal) lines. hypercementoss of tooth.

fig. 127 Paget's disease of bore.

fig 128 Pagefs disease of bone: 'mosaic' fig 129 Paget's disease: irregular

(reversal) lines. hypercementoss of tooth.

Radiation injury (osteoradionecrosis)

Irradiation for cancer can cause death of bone cells leaving empty lacunae (Fig. 130) and oblitcrativc endarteritis (Fig. 131), leaving severely ischaemic areas of bone. Attempts to separate this dead tissue by osteoclasts produce moth-eaten areas but this activity is limited by the poor blood supply. Infection, usually from teeth, readily spreads in the ischaemic bone and can give rise to extensive chronic osteomyelitis.

Osteomyelitis

Aenology Infection of the jaw can rarely result from severe dental infections or from fractures open to the skin, or it may be secondary to irradiation.

Microscopy Infection spreads through the cancellous spaces leading to thrombosis of blood vessels in bony canaliculae and bone necrosis. Necrotic bone shows empty lacunae, is typically infiltrated by inflammatory cells (Figs 132 & 133) and may show masses of bacteria. Osteoclasts from healthy peripheral bone resorb the junction with infected bone which becomes separated as a sequestrum.

Osteoradionecrosis The Jaw

Rg. 130 Osteoradionecrosis.

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